T-Mobile and Metro PCS customers have begun receiving notifications about a potential security breach where some personal information could have been compromised. T-Mobile starts by saying that out of "an abundance of caution" it is notifying the customers that are potentially affected. On August 20, our cyber-security team discovered and shut down an unauthorized access to certain information, including yours, and we promptly reported it to authorities. Fortunately, there is no financial data involved in the breach. Credit card numbers, bank account numbers, and social security numbers...
Source: https://www.gsmarena.com/tmobile_says_customer_data_was_exposed_in_the_latest_security_breach-news-32923.php